GB764798A - Improvements in or relating to tractors - Google Patents

Abstract

764,798. Tractor driving gear. INTERNATIONAL HARVESTER CO. Feb. 9, 1955 [March 17, 1954], No. 3842/55. Class 79(2). [Also in Group XXIX] In a tractor the primary drive shaft of a change speed gear may be driven from either end ; at the front end normal drive may be taken from the engine through a clutch while at the rear end drive may be taken from the engine by way of an auxiliary power transmission giving a reduction in transmission ratio which is additive to the ratios obtainable with the change speed gear. The auxiliary power transmission may be hydraulic or mechanical. The drawings show a tractor with an engine 11 and traction wheels 13 and 14 with driving axles 15, 16 mounted in a final drive housing 21. The crank shaft 23 of the engine is connected to a primary drive shaft 24 of a change speed gear box 25 through a main clutch 26. The gear box 25 has gear clusters 35 and 36 on the primary drive shaft 24, an idler gear 38 for reversing and a driven shaft 29 connected with the traction wheels 13, 14 by means of the bevel gear 45, 46 and a differential gear 47 driving coaxial shafts 48, 49 each of which drive a gear on a traction wheel axle shaft. A shaft 56 of a power take-off unit 54 is coupled at 57 to the primary drive shaft 24 of the gear box 25 and drives power take-off shafts 61 and 65. For the purposes of the invention the take-off shaft 65 is disengageably coupled at 67 to a shaft 69 to which an auxiliary drive may be applied to drive the primary drive shaft 24 of gear box 25 independently of the main clutch 26. The auxiliary drive may comprise an hydraulic pump 74 driven by the engine 11. A control valve 78 with a plunger 81 in the position shown connects conduits 76 and 83 to merely circulate fluid through a reservoir 84. When the plunger is moved to the right conduits 76 and 88 are connected to drive an hydraulic motor 89 which is adapted to drive the shaft 69, and hence shaft 24 of gear box 25. By making the motor 89 of large capacity as compared with the pump 74 and/or by selection of the gear ratios between the motor 89 and shaft 69 and/or the engine 11 and pump 74, a low ratio drive to the gear box is obtained to which the gear ratios of the gear box are additive. An alternative control valve 79a for the hydraulic pump 74 is shown in Fig. 2. Conduits 88a and 91a connect with the motor 89 and a check valve 119 limits the pressure between the conduits. The valve has positions for forward, neutral and reverse drives. In the neutral position shown the lands 108, 109 of the valve piston 107 are by-passed by channels 114 and 115 in the valve casing. For forward drive the reservoir 84 communicates with the valve chamber 117 through a passage 112 in the valve piston 107.